1. Field of the Invention
This invention relates to a nonwoven fabric containing a blend of hard and elastic staple fibers. In particular the invention concerns an improved process for making such a fabric in the form of a heat-treated, spunlaced structure which has improved physical and aesthetic characteristics.
2. Description of the Prior Art
Nonwoven fabrics made by hydraulic entanglement techniques are well known in the art, as for example, from U.S. Pat. Nos. 3,485,706 (Evans), 3,493,462 (Bunting et al.), 3,494,821 (Evans) and 3,560,326 (Bunting et al.). These patents disclose the impingement of fine columnar jets of liquid onto a fibrous batt supported on a foraminous member. This treatment entangles the fibers and converts the batt into a strong nonwoven fabric. Adhesive binders or self-bonding fibers are not necessary to hold the fibers together. Such fabrics have been referred to in commercial use, as well as in the technical literature, as spunlaced fabrics.
Fibers suitable for use in the starting batts of these spunlaced fabrics can be of one or more types and compositions. A wide range of fiber lengths is useful, from very short to substantially continuous. The resultant hydraulically entangled fabrics can be nonpatterned or have a repeating pattern of entangled fiber regions and interconnecting fiber regions, with or without a repeating pattern of apertures. It has also been suggested that by combining fibers of different compositions, melting or softening points, deniers, lengths or cross-sections, tactile aesthetics and physical properties of the fabric can be altered.
Many useful spunlaced fabrics have been prepared by the above-described hydraulic entanglement techniques. Numerous blends of different types of fibers have been found suitable for making a wide variety of spunlaced fabrics. Such fabrics have found application in a wide variety of uses and products. However, improvements in the stretch, resilience, crease resistance and other aesthetic characteristics of these fabrics would greatly enhance their utility and versatility. For example, strong, stretchable and resilient nonwoven fabrics are desired as substrates for use in vinyl-coated upholstery mterial. Nonwovens with such improved characteristics also would improve their utility in nonwoven industrial garments and increase their life in limited wear garments. The surface characteristics as well as the stretch, resilience and strength characteristics of spunlaced fabrics are of great importance to synthetic leather manufacturers and improvements in several of these characteristics would improve the usefulness of the substrate, as for example, in the manufacture of synthetic leather gloves, shoe uppers, and bags.
U.S. Pat. No. 3,485,706, Example 56, item "e," illustrates the fabrication of a bulky, puckered, spunlaced fabric having high elasticity in one direction. The structure is made up of two layers of polyester staple fibers, between which is a warp of spandex yarns of 70-denier, coalesced multifilaments. During the hydraulic entanglement step of the fabrication, the spandex yarns are prestretched 200%. The patent further suggests that any elastic fibers and/or yarns may be used in a tensioned warp or cross warp and that any fiber may be used in the surface layers to obtain a warp-reinforced spunlaced nonwoven fabric. Although such structures are technically feasible, the introduction of pretensioned warps into the hydraulic entanglement process results in technical complications and additional costs. Furthermore, well known spandex filaments or yarns which might be used in such fabrics generally are of high denier and lead to irregularities or "show through" of the pretensioned warps in the final product.
U.S. Pat. No. 3,007,227 (Moler) suggests that improved yarns, fabrics and other textile materials can be made with blends of intermingled fibers of staple length comprised of a major portion by weight of hard inelastic staple fibers and a minor portion of essentially straight elastomeric staple fibers. The patent discloses nonwoven fabrics can be made from such blends in the form of carded webs, Rando-Webber batts and mechanically needled felts. A felt made by mechanically needling a 75/25 blend of rabbit fur and synthetic elastomeric fibers is exemplified in Example VIII, wherein the elastic fiber is reported to increase the hardness and compactness of the felt, as well as its resistance to delamination, in comparison to a felt made of 100% rabbit fur.
The purpose of the present invention is to provide an improved process for preparing nonwoven fabrics containing elastic fibers and to provide an improved spunlaced nonwoven fabric thereby.